T-Mobile US accused AT&T and Verizon of attempting to handicap its ability to bid in a key mid-band spectrum auction in December, after they claimed the operator already holds more than regulators allow.

In a blog, T-Mobile CEO Mike Sievert (pictured) argued AT&T and Verizon want to hamper its participation in a planned sale of C-Band spectrum (3.7GHz to 4.2GHz) so “they can run the table unchecked”. Without a “fair, competitive” bidding process, he warned the US will reap lower auction proceeds and lose “the benefit of ensuring that spectrum is put to use, to drive competition, by those most motivated to do so”.

His comments come after AT&T and Verizon noted in filings to the Federal Communications Commission (FCC) that T-Mobile’s low- and mid-band holdings already exceed the agency’s spectrum screen, which sets ownership limits to prevent anti-competitive market effects.

AT&T pressed the FCC to clarify the policy, including how it will be applied to the auction and whether companies “will be permitted to continue to amass holdings” exceeding the limits.

Operators identified mid-band spectrum as key for 5G because it offers broad geographic coverage and capacity for high data rates.

A recent auction of spectrum in the shared 3.5GHz band raised $4.6 billion, but C-Band is viewed as even more valuable because it offers access to larger swathes of licensed spectrum; fewer restrictions on transmission power levels; and aligns with global 5G frequency allocations.

In a LinkedIn post last month, mobile network provider BitPath’s COO Sasha Javid explained the C-Band sale could raise between $19 billion and $38 billion, based on the previous sale’s prices.